Sex ratio is variable and increasingly male biased at two colonies of Magellanic Penguins

Sex ratios are commonly skewed and variable in wild populations, but few studies track temporal trends in this demographic parameter. We examined variation in the operational sex ratio at two protected and declining breeding colonies of Magellanic Penguins ( Spheniscus magellanicus ) in Chubut, Argentina. Penguins from the two colonies, separated by 105 km, migrate north in the non‐breeding season and have overlapping distributions at sea....